Ambient‐temperature copper‐catalyzed atom transfer radical polymerization of methacrylates in ethylene glycol solvents

The use of ethylene glycol solvents in the room‐temperature atom transfer radical polymerization (ATRP) of various hydrophobic and hydrophilic methacrylates is demonstrated. Unlike many of the very polar solvents described in the literature for room‐temperature ATRP, these solvents have good solvency for a wide range of polymers and monomers and are cheap and relatively nontoxic. Ethylene glycols with one hydroxyl and one methoxy group, such as tri(ethylene glycol) monomethyl ether (TEGMME), provide optimal results. The polymerization of methyl methacrylate in TEGMME with CuBr/N,N,N′N′,N″‐pentamethyldiethylenetriamine as the catalyst requires the addition of CuCl₂ at the beginning of the reaction to produce well‐controlled polymerizations. This leads to polymers with predictable molecular weights and relatively narrow polydispersities. Polymerization in solvents that are fully methoxy‐capped terminate prematurely because of catalyst precipitation. The electrochemical behavior of copper complexes in selected solvents is examined to determine why these solvents provide good rates at room temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1588–1598, 2005     

Synthesis of well‐defined 7‐arm and 21‐arm poly(N‐isopropylacrylamide) star polymers with β‐cyclodextrin cores via click chemistry and their thermal phase transition behavior in aqueous solution

The syntheses of well‐defined 7‐arm and 21‐arm poly(N‐isopropylacrylamide) (PNIPAM) star polymers possessing β‐cyclodextrin (β‐CD) cores were achieved via the combination of atom transfer radical polymerization (ATRP) and click reactions. Heptakis(6‐deoxy‐6‐azido)‐β‐cyclodextrin and heptakis[2,3,6‐tri‐O‐(2‐azidopropionyl)]‐β‐cyclodextrin, β‐CD‐(N₃)₇ and β‐CD‐(N₃)₂₁, precursors were prepared and thoroughly characterized by nuclear magnetic resonance and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. A series of alkynyl terminally functionalized PNIPAM (alkyne‐PNIPAM) linear precursors with varying degrees of polymerization (DP) were synthesized via atom transfer radical polymerization (ATRP) of N‐isopropylacrylamide using propargyl 2‐chloropropionate as the initiator. The subsequent click reactions of alkyne‐PNIPAM with β‐CD‐(N₃)₇ and β‐CD‐(N₃)₂₁ led to the facile preparation of well‐defined 7‐arm and 21‐arm star polymers, namely β‐CD‐(PNIPAM)₇ and β‐CD‐(PNIPAM)₂₁. The thermal phase transition behavior of 7‐arm and 21‐arm star polymers with varying molecular weights were examined by temperature‐dependent turbidity and micro‐differential scanning calorimetry, and the results were compared to those of linear PNIPAM precursors. The anchoring of PNIPAM chain terminal to β‐CD cores and high local chain density for star polymers contributed to their considerably lower critical phase separation temperatures (T_c) and enthalpy changes during phase transition as compared with that of linear precursors. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 404–419, 2009     

ABC‐type hetero‐arm star terpolymers through “Click” chemistry

Hetero‐arm star ABC‐type terpolymers, poly(methyl methacrylate)‐polystyrene‐poly(tert‐butyl acrylate) (PMMA‐PS‐PtBA) and PMMA‐PS‐poly(ethylene glycol) (PEG), were prepared by using “Click” chemistry strategy. For this, first, PMMA‐b‐PS with alkyne functional group at the junction point was obtained from successive atom transfer radical polymerization (ATRP) and nitroxide‐mediated radical polymerization (NMP) routes. Furthermore, PtBA obtained from ATRP of tBA and commercially available monohydroxyl PEG were efficiently converted to the azide end‐functionalized polymers. As a second step, the alkyne and azide functional polymers were reacted to give the hetero‐arm star polymers in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine ( PMDETA) in DMF at room temperature for 24 h. The hetero‐arm star polymers were characterized by ¹H NMR, GPC, and DSC. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5699–5707, 2006     

Well‐controlled ATRP of 2‐(2‐(2‐azidoethyoxy)ethoxy)ethyl methacrylate for high‐density click functionalization of polymers and metallic substrates

The combination of atom transfer radical polymerization (ATRP) and click chemistry has created unprecedented opportunities for controlled syntheses of functional polymers. ATRP of azido‐bearing methacrylate monomers (e.g., 2‐(2‐(2‐azidoethyoxy)ethoxy)ethyl methacrylate, AzTEGMA), however, proceeded with poor control at commonly adopted temperature of 50 °C, resulting in significant side reactions. By lowering reaction temperature and monomer concentrations, well‐defined pAzTEGMA with significantly reduced polydispersity were prepared within a reasonable timeframe. Upon subsequent functionalization of the side chains of pAzTEGMA via Cu(I)‐catalyzed azide‐alkyne cycloaddition (CuAAC) click chemistry, functional polymers with number‐average molecular weights (M_n) up to 22 kDa with narrow polydispersity (PDI < 1.30) were obtained. Applying the optimized polymerization condition, we also grafted pAzTEGMA brushes from Ti6Al4 substrates by surface‐initiated ATRP (SI‐ATRP), and effectively functionalized the azide‐terminated side chains with hydrophobic and hydrophilic alkynes by CuAAC. The well‐controlled ATRP of azido‐bearing methacrylates and subsequent facile high‐density functionalization of the side chains of the polymethacrylates via CuAAC offers a useful tool for engineering functional polymers or surfaces for diverse applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1268–1277     

Atom transfer radical polymerization of 6‐O‐methacryloyl‐1,2;3,4‐di‐O‐isopropylidene‐D‐galactopyranose in solution

A detailed exploration of the atom transfer radical polymerization (ATRP) of a sugar‐carrying monomer, 6‐O‐methacryloyl‐1,2;3,4‐di‐O‐isopropylidene‐D‐galactopyranose (MAIPGal) was performed. The factors pertinent to ATRP, such as initiators, ligands, catalysts, and temperature were optimized to obtain good control over the polymerization. The kinetics were examined in detail when the polymerization was initiated by methyl 2‐bromoisopropionate (2‐MBP), ethyl 2‐bromoisobutyrate (2‐EBiB), or a macroinitiator, [α‐(2‐bromoisobutyrylate)‐ω‐methyl PEO] (PEO–Br), with bipyridine (bipy) as the ligand at 60 °C or by 2‐EiBB with N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as the ligand at room temperature (23 °C). The effects of the catalysts (CuBr and CuCl) were also investigated. We demonstrate that the successful ATRP of MAIPGal can be achieved for 2‐EBiB/CuBr/bipy and 2‐MBP/CuCl/bipy at 60 °C and for 2‐EBiB/CuBr/PMDETA at room temperature. The initiation by 2‐EBiB at room temperature with PMDETA as the ligand should be the most optimum operation for its moderate condition and suppression of many side reactions. Chain extension of P(MAIPGal) prepared by ATRP with methyl methacrylate (MMA) as the second monomer was carried out and a diblock copolymer, P(MAIPGal)‐b‐PMMA, was obtained. Functional polymers, poly(D‐galactose 6‐methacrylate) (PGMA), PEO‐b‐PGMA, and PGMA‐b‐PMMA were obtained after removal of the protecting groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 752–762, 2005     

Synthesis of poly(β‐pinene)‐g‐poly(meth)acrylate by the combination of living cationic polymerization and atom transfer radical polymerization

New graft copolymers of β‐pinene with methyl methacrylate (MMA) or butyl acrylate (BA) were synthesized by the combination of living cationic polymerization and atom transfer radical polymerization (ATRP). β‐Pinene polymers with predetermined molecular weights and narrow molecular weight distributions (MWDs) were prepared by living cationic polymerization with the 1‐phenylethyl chloride/TiCl₄/Ti(OiPr)₄/nBu₄NCl initiating system, and the resultant polymers were brominated quantitatively by N‐bromosuccinamide in the presence of azobisisobutyronitrile, yielding poly(β‐pinene) macroinitiators with different bromine contents (Br/β‐pinene unit molar ratio = 1.0 and 0.5 for macroinitiators a and b , respectively). The macroinitiators, in conjunction with CuBr and 2,2′‐bipyridine, were used to initiate ATRP of BA or MMA. With macroinitiator a or b , the bulk polymerization of BA induced a linear first‐order kinetic plot and gave graft copolymers with controlled molecular weights and MWDs; this indicated the living nature of these polymerizations. The bulk polymerization of MMA initiated with macroinitiator a was completed instantaneously and induced insoluble gel products. However, the controlled polymerization of MMA was achieved with macroinitiator b in toluene and resulted in the desired graft copolymers with controlled molecular weights and MWDs. The structures of the obtained graft copolymers of β‐pinene with (methyl)methacrylate were confirmed by ¹H NMR spectra. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1237–1242, 2003     

Multifunctional ATRP initiators: Synthesis of four‐arm star homopolymers of methyl methacrylate and graft copolymers of polystyrene and poly(t‐butyl methacrylate)

Tetrakis bromomethyl benzene was used as a tetrafunctional initiator in the synthesis of four‐armed star polymers of methyl methacrylate via atom transfer radical polymerization (ATRP) with a CuBr/2,2 bipyridine catalytic system and benzene as a solvent. Relatively low polydispersities were achieved, and the experimental molecular weights were in agreement with the theoretical ones. A combination of 2,2,6,6‐tetramethyl piperidine‐N‐oxyl‐mediated free‐radical polymerization and ATRP was used to synthesize various graft copolymers with polystyrene backbones and poly(t‐butyl methacrylate) grafts. In this case, the backbone was produced with a 2,2,6,6‐tetramethyl piperidine‐N‐oxyl‐mediated stable free‐radical polymerization process from the copolymerization of styrene and p‐(chloromethyl) styrene. This polychloromethylated polymer was used as an ATRP multifunctional initiator for t‐butyl methacrylate polymerization, giving the desired graft copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 650–655, 2001     

Novel synthesis of rod‐coil block copolymers by combination of coordination polymerization and ATRP

Combination of coordination polymerization and atom transfer radical polymerization (ATRP) was applied to a novel synthesis of rod‐coil block copolymers. The procedure included the following steps: (1) monoesterification reaction of ethylene glycol with 2‐bromoisobutyryl bromide yielded a α‐bromo, ω‐hydroxy bifunctional initiator, (2) CpTiCl₃ (bifunctional initiator) catalyst was prepared from a mixture of trichlorocyclopentadienyl titanium (CpTiCl₃) and bifunctional initiator. Coordination polymerization of n‐butyl isocyanate initiated by such catalyst provided a well‐defined macroinitiator, poly(n‐butyl isocyanate)‐Br (PBIC‐Br), and (3) ATRP method of vinyl monomers using PBIC‐Br provided rod (PBIC)‐coil block copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4037–4042, 2007     

R‐RAFT approach for the polymerization of N‐isopropylacrylamide with a star poly(ε‐caprolactone) core

Reversible addition‐fragmentation chain transfer (RAFT) polymerization is a more robust and versatile approach than other living free radical polymerization methods, providing a reactive thiocarbonylthio end group. A series of well‐defined star diblock [poly(ε‐caprolactone)‐b‐poly(N‐isopropylacrylamide)]₄ (SPCLNIP) copolymers were synthesized by R‐RAFT polymerization of N‐isopropylacrylamide (NIPAAm) using [PCL‐DDAT]₄ (SPCL‐DDAT) as a star macro‐RAFT agent (DDAT: S‐1‐dodecyl‐S′‐(α, α′‐dimethyl‐α″‐acetic acid) trithiocarbonate). The R‐RAFT polymerization showed a controlled/“living” character, proceeding with pseudo‐first‐order kinetics. All these star polymers with different molecular weights exhibited narrow molecular weight distributions of less than 1.2. The effect of polymerization temperature and molecular weight of the star macro‐RAFT agent on the polymerization kinetics of NIPAAm monomers was also addressed. Hardly any radical–radical coupling by‐products were detected, while linear side products were kept to a minimum by careful control over polymerization conditions. The trithiocarbonate groups were transferred to polymer chain ends by R‐RAFT polymerization, providing potential possibility of further modification by thiocarbonylthio chemistry. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterizations of the four‐armed amphiphilic block copolymer S[poly(2,3‐dihydroxypropyl acrylate)‐block‐poly(methyl acrylate)]4

The polymers poly[(2,2‐dimethyl‐1,3‐dioxolane‐4yl) methyl acrylate] (PDMDMA) and four‐armed PDMDMA with well‐defined structures were prepared by the polymerization of (2,2‐dimethyl‐1,3‐dioxolane‐4yl) methyl acrylate (DMDMA) in the presence of an atom transfer radical polymerization (ATRP) initiator system. The successive hydrolyses of the polymers obtained produced the corresponding water‐soluble polymers poly(2,3‐dihydroxypropyl acrylate) (PDHPA) and four‐armed PDHPA. The controllable features for the ATRP of DMDMA were studied with kinetic measurements, gel permeation chromatography (GPC), and NMR data. With the macroinitiators PDMDMA–Br and four‐armed PDMDMA–Br in combination with CuBr and 2,2′‐bipyridine, the block polymerizations of methyl acrylate (MA) with PDMDMA were carried out to afford the AB diblock copolymer PDMDMA‐b‐MA and the four‐armed block copolymer S{poly[(2,2‐dimethyl‐1,3‐dioxolane‐4yl) methyl acrylate]‐block‐poly(methyl acrylate)}₄, respectively. The block copolymers were hydrolyzed in an acidic aqueous solution, and the amphiphilic diblock and four‐armed block copolymers poly(2,3‐dihydroxypropyl acrylate)‐block‐poly(methyl acrylate) were prepared successfully. The structures of these block copolymers were verified with NMR and GPC measurements. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3062–3072, 2001     

Atom transfer radical polymerization of sodium2‐acrylamido‐2‐methylpropanesulfonate

The first example of well‐controlled atom transfer radical polymerization (ATRP) of a permanently charged anionic acrylamide monomer is reported. ATRP of sodium 2‐acrylamido‐2‐methylpropanesulfonate (NaAMPS) was achieved with ethyl 2‐chloropropionate (ECP) as an initiator and the CuCl/CuCl₂/tris(2‐dimethylaminoethyl)amine (Me₆TREN) catalytic system. The polymerizations were carried out in 50:50 (v/v) N,N‐dimethylformamide (DMF)/water mixtures at 20 °C. Linear first‐order kinetic plots up to a 92% conversion for a target degree of polymerization of 50 were obtained with [ECP]/[CuCl]/[CuCl₂]/[Me₆TREN] = 1:1:1:2 and [AMPS] = 1 M. The molecular weight increased linearly with the conversion in good agreement with the theoretical values, and the polydispersities decreased with increasing conversion, reaching a lower limit of 1.11. The living character of the polymerization was confirmed by chain‐extension experiments. Block copolymers with N,N‐dimethylacrylamide and N‐isopropylacrylamide were also prepared. The use of a DMF/water mixed solvent should make possible the synthesis of new amphiphilic ionic block copolymers without the use of protecting group chemistry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4446–4454, 2005     

Synthesis of multiarmed poly(3‐hexyl thiophene) star polymer with microgel core by GRIM and ATRP methods

Regioregular poly(3‐hexyl thiophene) (rr‐P3HT)‐based star polymers were synthesized by a crosslinking reaction of the linear rr‐P3HT macroinitiator and ethylene glycol dimethacrylate (EGDMA) crosslinker through Ru‐based atom transfer radical polymerization (ATRP), where the rr‐P3HT macroinitiator was prepared by Grignard metathesis method (GRIM) followed by end functionalization of the ATRP initiator with chlorophenylacetate (CPA) to the rr‐P3HT. Relatively high molecular weight of the star polymers were obtained (M_p = 8,988,000 g/mol), which consisted of large numbers of the rr‐P3HT arm chains radiating from the EGDMA‐based microgel core. The yield of the star polymers were strongly affected by the added amount of the EGDMA crosslinker. The crystalline structure of the rr‐P3HT by intermolecular π‐π stacking interaction gradually decreased as the star polymer formed, which was confirmed by differential scanning calorimeter (DSC), atomic force microscopy (AFM), and electro‐optical analyses. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of liquid crystalline side‐chain block copolymers containing luminescent 4,4′‐bis(biphenyl)fluorene pendants

A series of new liquid crystalline homopolymers, copolymers, and block copolymers were polymerized from styrene‐macroinitiator ( SMi ) and methacrylates with pendent 4,4′‐bis(biphenyl)fluorene ( M1 ) and biphenyl‐4‐ylfluorene ( M2 ) groups through atom transfer radical polymerization (ATRP). The number‐average molecular weights (Mn) of polymers P1 ‐ P4 were 10,007, 14,852, 6,275, and 10,463 g mol^?1 with polydispersity indices values of 1.21, 1.15, 1.31, and 1.22, respectively. All polymers exhibit the nematic phase. The thermal, mesogenic, and photoluminescent properties of all polymers were investigated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4564–4572, 2007     

Atom transfer radical polymerization of styrene using the novel initiator ethyl 2‐N,N‐(diethylamino)dithiocarbamoyl‐butyrate

The atom transfer radical polymerizations (ATRPs) of styrene initiated by a novel initiator, ethyl 2‐N,N‐(diethylamino)dithiocarbamoyl‐butyrate (EDDCB), in both bulk and solution were successfully carried out in the presence of copper(I) bromide (CuBr) and N,N,N′,N″,N″‐pentamethyldiethylenetriamine at 115 °C. The polymerization rate was first‐order with respect to the monomer concentration, and the molecular weights of the obtained polymers increased linearly with the monomer conversions with very narrow molecular weight distributions (as low as 1.17) up to higher conversions in both bulk and solution. The polymerization rate was influenced by various solvents in different degrees in the order of cyclohexanone > dimethylformamide > toluene. The molecular weight distributions of the produced polymers in cyclohexanone were higher than those in dimethylformamide and toluene. The results of ¹H NMR analysis and chain extension confirmed that well‐defined polystyrene bearing a photo‐labile N,N‐(diethylamino)dithiocarbamoyl group was obtained via ATRP of styrene with EDDCB as an initiator. The polymerization mechanism for this novel initiation system is a common ATRP process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 32–41, 2006     

Fluorinated bio‐acceptable polymers via an ATRP macroinitiator approach

Polymers derived from bio‐acceptable poly(methyl methacrylate) (PMMA), poly(2‐methoxyethyl acrylate) (PMEA), and poly(oligo(ethylene glycol) methyl ether methacrylate) (PPEGMA) have been prepared via atom transfer radical polymerization (ATRP) utilizing an initiator prepared from a fluoroalkoxy‐terminated oligoethylene glycol. Polymerizations are controlled as seen by both linear first‐order kinetics and molecular weight evolution coupled with low polydispersities (<1.25) with respect to conversion. A range of ligands have been used depending upon the nature of the monomer: N‐(n‐propyl)‐2‐pyridyl‐methanimine with the methacrylates MMA and PEGMA and 1,1,4,7,10,10‐hexamethyltriethylene tetramine (HMTETA) with MEA. In all cases the use of the fluorinated initiator results in a lower apparent rate of propagation (k_p^app) as compared with the more conventional and nonfluorinated initiator, ethyl 2‐bromoisobutyrate. The initiator generally also serves as an internal plasticizer lowering the glass transition temperature from the parent polymers. The surface characteristics of the fluoroinitiator containing polymers are altered compared with the nonfluorinated analogues. This is reflected in a significant increase in the advancing water contact angles of all fluoro‐containing polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5770–5780, 2007     

Synthesis of PS‐b‐PPOA‐b‐PS triblock copolymer via sequential free radical polymerization and ATRP

A novel ABA triblock copolymer comprising double‐bond‐containing poly(phenoxyallene) (PPOA) and polystyrene (PS) segments was synthesized by sequential conventional free radical polymerization and atom transfer radical polymerization (ATRP) via the site transformation strategy. A new bifunctional initiator containing azo and Br‐containing ATRP initiating groups was prepared using 2‐bromopropionyl chloride, hydroquinone, and 4,4′‐azobis(4‐cyanopentanoic acid) as starting materials. Conventional free radical homopolymerization of phenoxyallene with cumulated double bond was performed in toluene to provide a polyallene‐based macroinitiator bearing ATRP initiating groups at both ends, which is stable under UV irradiation and free radical circumstances. PS‐b‐PPOA‐b‐PS triblock copolymer was then obtained by bulk ATRP of styrene initiated by PPOA‐based macroinitiator. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1366–1372     

Synthesis and chiral recognition ability of optically active poly{N‐[(R)‐α‐methoxycarbonylbenzyl]methacrylamide} with various tacticities by radical polymerization using Lewis acids

The radical polymerization of an optically active methacrylamide, N‐[(R)‐α‐methoxycarbonylbenzyl]methacrylamide, was carried out in the absence and presence of Lewis acids such as yittribium trifluoromethanesulfonate [Yb(OTf)₃] and scandium trifluoromethanesulfonate [Sc(OTf)₃]. Catalytic amounts of the Lewis acids significantly affected the stereoregularity of the obtained polymers. The polymerization with Yb(OTf)₃ in tetrahydrofuran afforded isotactic polymers (up to mm = 87%), whereas the conventional radical method without the Lewis acid produced polymers rich in syndiotacticity (up to rr = 88%). The radical polymerization in the presence of MgBr₂ proceeded in a heterotactic‐selective manner (mr = 63%). Thus, the isotactic, syndiotactic, and heterotactic poly(methacrylamide)s were synthesized by the radical processes. The chiral recognition abilities of the obtained optically active poly(methacrylamide)s were affected by the stereoregularity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3354–3360, 2003     

Dual thermo‐ and pH‐sensitive network‐grafted hydrogels formed by macrocrosslinker as drug delivery system

Dual thermo‐ and pH‐sensitive network‐grafted hydrogels made of poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) network and poly(N‐isopropylacrylamide) (PNIPAM) grafting chains were successfully synthesized by the combination of atom transfer radical polymerization (ATRP), reversible addition‐fragmentation chain transfer (RAFT) polymerization, and click chemistry. PNIPAM having two azide groups at one chain end [PNIPAM‐(N₃)₂] was prepared with an azide‐capped ATRP initiator of N,N‐di(β‐azidoethyl) 2‐chloropropionylamide. Alkyne‐pending poly(N,N‐dimethylaminoethyl methacrylate‐co‐propargyl acrylate) [P(DMAEMA‐co‐ProA)] was obtained through RAFT copolymerization using dibenzyltrithiocarbonate as chain transfer agent. The subsequent click reaction led to the formation of the network‐grafted hydrogels. The influences of the chemical composition of P(DMAEMA‐co‐ProA) on the properties of the hydrogels were investigated in terms of morphology and swelling/deswelling kinetics. The dual stimulus‐sensitive hydrogels exhibited fast response, high swelling ratio, and reproducible swelling/deswelling cycles under different temperatures and pH values. The uptake and release of ceftriaxone sodium by these hydrogels showed both thermal and pH dependence, suggesting the feasibility of these hydrogels as thermo‐ and pH‐dependent drug release devices. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of well‐defined AB20‐type star polymers with cyclodextrin‐core by combination of NMP and ATRP

The synthesis of an AB₂₀‐type heteroarm star polymer consisting of a polystyrene arm and 20‐arms of poly(methyl methacrylate) or poly(tert‐butyl acrylate) was carried out using the combination of nitroxide‐mediated polymerization (NMP) and atom transfer radical polymerization (ATRP). The NMP of styrene was carried out using mono‐6‐[4‐(1′‐(2″,2″,6″,6″‐tetramethyl‐1″‐piperidinyloxy)‐ethyl)benzamido]‐β‐cyclodextrin peracetate ( 1 ) to afford end‐functionalized polystyrene with an acetylated β‐cyclodextrin (β‐CyD) unit (prepolymer 2 ) with a number‐average molecular weight (M_n) of 11700 and a polydispersity (M_w/M_n) of 1.17. After deacetylation of prepolymer 2 , the resulting polymer was reacted with 2‐bromoisobutyric anhydride to give end‐functionalized polystyrene with 20(2‐bromoisobutyrol)s β‐CyD, macroinitiator 4 . The copper (I)‐mediated ATRP of methyl methacrylate (MMA) and tert‐butyl acrylate (tBA) was carried out using macroinitiator 4 . The resulting polymers were isolated by SEC fractionation to produce AB₂₀‐type star polymers with a β‐CyD‐core, 5 . The well‐defined structure of 5 with weight‐average molecular weight (M_w)s of 13,500–65,300 and M_w/M_n's of 1.26–1.28 was demonstrated by SEC and light scattering measurements. The arm polymers were separated from 5 by destruction with 28 wt % sodium methoxide in order to analyze the details of their characteristic structure. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4271–4279, 2005     

Facile synthesis of AB2‐type miktoarm star polymers through the combination of atom transfer radical polymerization and ring‐opening polymerization

A novel miktofunctional initiator ( 1 ), 2‐hydroxyethyl 3‐[(2‐bromopropanoyl)oxy]‐2‐{[(2‐bromopropanoyl)oxy]methyl}‐2‐methyl‐propanoate, possessing one initiating site for ring‐opening polymerization (ROP) and two initiating sites for atom transfer radical polymerization (ATRP), was synthesized in a three‐step reaction sequence. This initiator was first used in the ROP of ?‐caprolactone, and this led to a corresponding polymer with secondary bromide end groups. The obtained poly(?‐caprolactone) (PCL) was then used as a macroinitiator for the ATRP of tert‐butyl acrylate or methyl methacrylate, and this resulted in AB₂‐type PCL–[poly(tert‐butyl acrylate)]₂ or PCL–[poly(methyl methacrylate)]₂ miktoarm star polymers with controlled molecular weights and low polydispersities (weight‐average molecular weight/number‐average molecular weight < 1.23) via the ROP–ATRP sequence. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2313–2320, 2004